Electromagnetic actuator

Abstract

An electromagnetic actuator comprises: a magnet; a pole piece mounted to the magnet; a yoke facing the pole piece; a coil base having a vibration coil; leaf springs for supporting the coil base and a weight; a case for enclosing them; a cover for covering one side of the case; and a diaphragm having a voice coil, wherein the arms of the coil base are inserted through notches formed in the yoke, and the vibration coil and the voice coil is disposed in a gap in which the pole piece and the yoke face each other. The weight vibrates by the application of a low-frequency current to the vibration coil, and the diaphragm vibrates by the application of a high-frequency current to the voice coil.

What is claimed is:  
     
       1. An electromagnetic actuator comprising: (a) a magnet; (b) a pole piece mounted on the magnet; (c) a yoke facing the pole piece; (d) a coil base having a vibration coil facing the pole piece mounted thereon; (e) a leaf spring supporting the coil base; (f) a weight disposed around the periphery of the yoke and supported by the leaf spring, said weight vibrating responsive to excitation of the vibration coil; (g) a voice coil facing the pole piece; (h) a case enclosing (a) through (g); (i) a cover covering one side of the case; and (j) a diaphragm which vibrates responsive to excitation of the voice coil, wherein 
       the arms of the coil base are inserted through notches formed in the yoke, the vibration coil and the voice coil being disposed in a gap between the pole piece and a face of the yoke.  
     
     
       2. The electromagnetic actuator according to  claim 1 , wherein 
       the pole piece is formed of two pieces mounted on opposing sides of the magnet;  
       the vibration coil is disposed within the gap at one end of the gap; and  
       the voice coil is disposed within the gap at another end of the gap.  
     
     
       3. The electromagnetic actuator according to  claim 1 , 
       wherein the vibration coil and the voice coil are concentrically disposed in the gap.  
     
     
       4. The electromagnetic actuator according to  claim 1 , wherein two leaf springs support only one side of the weight. 
     
     
       5. The electromagnetic actuator according to  claim 1 , wherein the cover and the yoke are provided with fan-shaped notches and projections which are fitted to each other. 
     
     
       6. The electromagnetic actuator according to  claim 4 , wherein the two leaf springs are used as electric supply terminals. 
     
     
       7. The electromagnetic actuator according to  claim 6 , wherein the coil base is a resin molding and insulates the two leaf springs from each other. 
     
     
       8. The electromagnetic actuator according to  claim 1 , wherein the weight is a molding produced by sintering high-specific gravity powder. 
     
     
       9. The electromagnetic actuator according to  claim 1  wherein the diaphragm closes a second side of the case, opposite the cover. 
     
     
       10. An electromagnetic actuator comprising: (a) a magnet; (b) a pole piece mounted on the magnet; (c) a central yoke facing the pole piece and defining an inner gap therebetween; (d) a voice coil mounted within the inner gap; (e) an outer yoke facing the pole piece and defining an outer gap therebetween; (t) a vibration coil mounted within the outer gap; (g) a weight which vibrates responsive to excitation of the vibration coil; (h) a leaf spring supporting said weight; (i) a case enclosing (a) through (h); and (j) a diaphragm which vibrates responsive to excitation of the voice coil, wherein 
       a first magnetic circuit is formed from the pole piece toward the center via the central yoke and the case with the inner gap therebetween; and  
       a second magnetic circuit is formed from the pole piece toward the outer periphery via the outer yoke and the case with the outer gap therebetween.  
     
     
       11. The electromagnetic actuator according to  claim 10 , wherein a direction regulating member is provided along the inner periphery of the weight to regulate the direction of vibration of the weight. 
     
     
       12. The electromagnetic actuator according to  claim 10 , wherein the diaphragm closes one side of the case. 
     
     
       13. An electromagnetic actuator comprising: (a) a magnet; (b) a pole piece mounted on the magnet; (c) a peripheral yoke facing the pole piece around the outer periphery of the pole piece and defining an outer gap therebetween; (d) a voice coil facing the pole piece and mounted within the outer gap; (e) a center yoke facing an inner peripheral surface of the pole piece and defining an inner gap therebetween; (f) a vibration coil facing the pole piece and mounted within the inner gap; (g) a weight which vibrates responsive to excitation of the vibration coil; (h) a leaf spring supporting the weight; (i) a case supporting the magnet and enclosing (a) through (h); and (j) a diaphragm which vibrates responsive to excitation of the voice coil, wherein 
       a first magnetic circuit is formed from the pole piece toward the outer periphery via the peripheral yoke and the case with the outer gap sandwiched therebetween; and  
       a second magnetic circuit is formed from the pole piece toward the center via the center yoke and the case with the inner gap sandwiched therebetween.  
     
     
       14. The electromagnetic actuator according to  claim 13 , wherein a direction regulating member is provided along the inner periphery of the weight to regulate the direction of vibration of the weight. 
     
     
       15. The electromagnetic actuator according to  claim 13 , wherein the diaphragm closes one side of the case.